The structure of a basic PLED display device can be extremely simple, consisting of a sandwich containing:

• A transparent electrode with a large work function. Indium tin oxide (ITO) is commonly used.
• A layer of PLED material less than 100nm thick
• A metallic electrode with a low work function, typically calcium.

A voltage is applied across the contacts, creating an electric field and injecting charges into the polymer where they recombine and emit light.

In a very short time polymer light emitting materials have reached a performance level comparable with inorganic LEDs. They also have the fast switching speeds typical of LEDs (and around a thousand times faster than LCDs!).

Since the first devices were fabricated, very rapid progress has been made in improving the quantum efficiencies of PLED devices.

Initially, internal quantum efficiencies of only 0.01% were achieved (defined as the number of photons generated in the polymer film relative to the number of carriers injected into the polymer). Today, figures three orders of magnitude higher have been reported.

These improvements have been achieved in part by utilising device engineering techniques learnt during the improvement in efficiencies of inorganic LEDs such as GaAs. In particular, the use of a heterostructure that allows carrier confinement at the polymer/polymer interface is significant. This increases the likelihood of electron/hole capture to form an exciton that can radiatively recombine. Other significant improvements arise from choosing the electron/hole injection barriers to be similar - this can be done through both the choice of the injection electrode material and by modifying the polymer material to be more or less electron withdrawing and therefore to have higher or lower electron affinity.